LED symbol signal

ABSTRACT

A LED symbol signal with LEDs arrayed to correspond to a desired symbol. A mask defines the desired symbol. A diffusion surface on the cover diffuses the display aspect, obscuring the individual LEDs. The mask is spaced a distance from the diffusing surface. The more aggressive the diffusion pattern the closer the mask is spaced to the diffusion pattern. Preferably, the ratio of the pitch of the optical elements to the width of the symbol at the diffusion surface is less than 1:2, preferably less than 1:4, more preferably less than 1:6 and most preferably approximately 1:10.

This application is a continuation in part of U.S. application Ser. No.10/122,576 filed on Apr. 15, 2002 that claims the benefit of U.S.provisional application 60/283,882, filed Apr. 13, 2001 and U.S.provisional application 60/361,140, filed Mar. 1, 2002, bothapplications hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to light emitting diode (LED) signals,specifically to an LED symbol signal with a uniform display aspectdespite having a reduced number of LEDs.

2. Description of Related Art

Symbol signals, for example turn signals, pedestrian signals, andwalk/don't walk signals previously have been designed with incandescentpoint light sources in a housing with a mask covering. The mask definingthe symbol desired. Incandescent bulbs suffer from drawbacks of highpower consumption and the requirement for frequent maintenance as thebulbs burn out.

LED symbol signals have reduced maintenance and operating costs due tothe extreme life span of LEDs and their low power consumption incomparison to incandescent bulbs. Previously, LEDs were used to form thesymbol desired by filling the symbol space with a full matrix of LEDs.As new, improved generations of LEDs become available, they emit morelight from each individual LED. Therefore, the full matrix of LEDs isnot required to create a suitably bright signal. The LEDs may then bespaced further apart from each other, omitting LEDs thereby savingmaterial costs and lowering the signals operating power consumption.However, as the LEDs spacing increases, an undesirably “pixel effect”appears in which the individual LEDs become increasingly discernable tothe viewer.

An object of the present invention is to provide a high efficiency andcost effective LED symbol with a reduced or eliminated “pixel effect”. Afurther object of this invention is to provide a LED symbol signal witha design that may be easily modified as new generations of LEDs withincreased light output become available, reducing the number of LEDsrequired to achieve a similar light output level.

An object of the present invention is to provide a high efficiency costeffective LED symbol with reduced sun phantom effect.

SUMMARY OF THE INVENTION

A LED symbol signal with LEDs arrayed to correspond to a desired symbol.Light from the LEDs is directed onto corresponding optical segments of amultiple collimating zone element and directed into a forwarddirection/distribution. A mask defines the desired symbol. The opticalsegments and or a diffusion surface on the cover or multiple collimatingzone element(s) diffuses the display aspect, obscuring the individualLEDs. A diameter of the optical features of the diffusion surface issmaller than a diameter of the optical segments. The LED symbol signalmay be configured for retrofitting into an incandescent lamp signalhousing.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is an isometric exploded view of a thick mask embodiment of theinvention.

FIG. 1B is an isometric exploded view of a thin mask embodiment of theinvention.

FIG. 2A is an isometric cut-away side view of a thin mask embodiment ofthe invention, showing light paths through the optical elements(electrical components omitted for clarity).

FIG. 2B is an isometric cut-away side view of a thick mask embodiment ofthe invention.

FIG. 3A is a side view of the embodiment shown in FIG. 2A, withincreased component details.

FIG. 3B is a side view of the embodiment shown in FIG. 2B, withincreased component details.

FIG. 4A is a schematic view of optical segments showing LED lightdistribution falling within the associated optical segments.

FIG. 4B is a schematic view of optical segments showing LED lightdistribution falling outside the associated optical segments.

FIG. 5A is a schematic view of hexagonal optical segments.

FIG. 5B is a schematic view of a human figure composed of hexagonaloptical segments.

FIG. 6A is a schematic view of a PCB board for an arrow symbol signal.

FIG. 6B is a schematic view of a bulk PCB showing the layout thereon ofmultiple PCB's according to FIG. 6A thereon.

FIG. 7 is a perspective view of the invention inserted in anincandescent signal with the incandescent bulb and lens removed.

FIG. 8 is a partial side view of one embodiment of the invention showingthe dimensional relationships of the invention elements.

FIG. 9 is an isometric cut-away view of a thick mask embodiment of theinvention using a reflector.

FIG. 10 is an isometric cut-away side view of an alternative embodimentof the invention.

FIG. 11 is a side view of the embodiment shown in FIG. 10.

FIG. 12A is a cross section an alternative embodiment of a diffusionsurface.

FIG. 12B is a cross section of a second alternative embodiment of adiffusion surface.

KEY TO FIGURE ELEMENTS

-   -   1—Cover    -   2—Mask    -   3—MCZE    -   4—Housing    -   5—PCB    -   6—Nut    -   7—Lock washer    -   8—LED(S)    -   9—Electrical components    -   10—Power connection    -   11—Post    -   12—PCB screw    -   13—Power supply wires    -   14—Screw    -   15—Electrical connection cover    -   16—Electrical connection screw    -   17—Incandescent socket power connector    -   18—Optical segment    -   19—Diffusion pattern    -   20—LED light emission pattern    -   21—O-ring    -   22—Bulk PCB panel    -   23—Reflector    -   24—Diffusion surface    -   25—Optical element

DETAILED DESCRIPTION

LED signals are disclosed in detail in U.S. patent application Ser. No.09/756,670, now U.S. Pat. No. 6,509,840, filed Jan. 9, 2001 and furtherin U.S. patent application Ser. No. 09/827,429, filed Apr. 6, 2001, bothapplications assigned to Applicant, GELcore LLC, and hereby incorporatedby reference in their entirety.

One embodiment of the present invention is shown in FIG. 1A. A printedcircuit board (PCB) 5 includes power supply circuitry and LEDs 8 groupedin clusters of at least one LED 8 each, arranged in the form of adesired symbol, here a directional arrow. The PCB 5 is mounted in ahousing 4 with integral power connection 10. As shown in FIG. 7, thehousing 4 may be dimensioned to permit retrofitting of the inventioninto existing incandescent light signal housings upon removal of theoriginal incandescent light bulb and lens(es). Power connection toexisting signal housing may be via an incandescent socket powerconnector 17. Use of the socket power connector 17 removes the need forelectricians to be involved in signal retrofitting activities. Mountedin/on the housing 4 spaced away from the PCB 5 is an optical element inthe form of a multiple collimated zone element (MCZE) 3. Portions of theMCZE 3, not desired as part of the symbol are covered by a mask 2. Thehousing is closed by a cover 1.

MCZE 3 has optical segments 18 (collimating zones) matching thedistribution of the LED 8 and/or LED 8 clusters on the PCB 5. As shownin FIG. 2A, each optical segment 18 collimates the light emitted fromits respective LED 8 or LED 8 cluster. Also, each optical segment 18 mayspread the light output into a desired distribution pattern. The effectof the MCZE 3 being to collect light from multiple point sources, eachLED 8 cluster, and distribute it evenly so that the pixel effect of theindividual LEDs 8 is minimized or removed from the display aspectobserved by a view. As shown in FIG. 4A, it is preferred that ratherthan overlapping with a neighboring segment as shown in FIG. 4B, thatthe light patter 20 from each LED/LED cluster fall within a singleoptical segment 18. As shown in FIG. 8, tuning of the Led light emissionpattern 20 to fall within an optical segment 18 diameter 0 and thedistance H between the PCB 5 and the MCZE 3. For large symbol areas, forexample in a walk/don't walk symbol, the MCZE 3 optical segments 18 maybe formed in a hexagonal shape, as shown in FIGS. 5A and 5B. Thehexagonal shape minimizing shadows or dark areas as it approximates thecircular light emission pattern 20 of the LED(s) 8. Where the opticalsegments 18 are on an outside edge, rather than forming the outer edgein the hexagonal form, a circular outside edge maximizes coverage.

A diffusion pattern 19 on the inner or outer surface of the MCZE 3 or onan inner or outer surface of the cover 1 may be used to further obscurediscernability of individual LEDs 8 in the display aspect. The diffusionpattern may be composed of circular, rectilinear or other geometricforms. Also, the diffusion pattern 19 may be formed on the desiredsurface via abrasion, impact and/or sandblasting. The diffusion pattern19 preferably has individual diffusion element diameters D in a lessthan 1 to 1 ratio to the diameter O of the associated optical segments18.

Cover 1 provides an environmental seal for the signal. A flat or a largeradius outer surface on cover 1 prevents dirt build-up on the MCZE 3.Sealing means, for example on o-ring 21, between the cover 1 and housing4 seals the signal from the environment.

Mask 2 may be integrated with the MCZE 3 and/or with the cover 1. Themask 2 may be in the form of a dark or opaque material, created viainsert film molding, tape, paint coating or other means for blocking theLed 8 light not passing through the optical segments 18.

To increase the symbol definition and minimize spurious light emissions,the mask 2 may be designed with a depth M that substantially fills thespace between the MCZE 3 and the cover 1 (FIGS. 1A, 2B, 3B).

MCZE 3 may be a full disk or other shape dimensioned to cover the openend of the housing, with optical segments formed thereon or there may bediscrete elements snap-fitting for example, into openings in the mask 2.For highest economy of materials, the cover 1, mask 2 and MCZE 3 may beintegrated into a single component.

To combat sun phantom effect, the cover 1 may include an angled outersurface. Also, the diffusion patter may be limited to only those areasin alignment within apertures in the mask 2 which define the desiredsymbol.

In an alternative embodiment, the signal has a cover 1 with a pluralityof optical elements 25 on at least one surface. There is no MCZE in thisembodiment. In the preferred embodiment the optical elements are on theinside surface of the cover and the outside surface is substantiallysmooth. In the preferred embodiment the optical elements are a diffusionpattern that covers substantially the entire inside surface of the cover1.

When sun hits the lens, it can reflect back and a viewer may see asignal as on even when it is off. This sun phantom effect is obvious forsymbols such as arrows and pedestrian signals. The symbol appears liteven when it is off. Lensing can exacerbate the effect. The sun reflectsoff the lens and/or the cup of the LEDs. Further, if a diffusion patternis limited to the areas in alignment with the symbol, reflection canalso have the appearance of an on signal.

To reduce the sun phantom effect, a diffusing surface is coupled with amask 2. The mask 2 is spaced a distance D1 from the diffusing surface24. The mask 2 is spaced a distance D2 from the PCB 5 or the LED base.The mask has an opening of width D3. The symbol at the diffusion surfacehas a width D4 which is larger than D3. The light appears to begenerated from the diffusing surface. For example, for a 12-inch signal,an arrow symbol having a width D4 of 1 inch the width D3 of the maskopening would be less than 1 inch.

The optical elements 25 that make up the diffusion pattern can becircular, rectilinear, or other geometric forms with spherical, arc, orstraight-line faces being the preferred shapes. The optical elements 25have a pitch P, which is the distance between 2 elements and a radius R.

The size of the optical elements effects the definition of the signal.The more aggressive the diffusing pattern, the closer the mask may be tothe pattern to improve the signal definition. The smoother the diffusingsurface, the further the mask should be placed from the diffusingsurface. It is preferred that the ratio of the distance between opticalelements and the signal width, P/D4 be a ratio of less than ½. Morepreferably less than ¼, 1/5 or ⅙. Most preferably, the ratio of P/D4 isapproximately 1/10. For example, for a 12-inch signal with a 1-incharrow the pitch is preferably approximately 0.1 inch. If the ratiobecomes too small, other optical effects are seen.

Preferably narrow spread LEDs are used in this embodiment. Morepreferably LEDs which emit light in a 15 degree-20 degree spread arepreferred. The light from the narrow spread LED is spread by thediffusion surface. Preferably, the light is spread to 30 degrees. Thewider the spread of the LED the lower the light intensity. Choosing anLED with a narrow light pattern allows the signal to have the requiredon-axis intensity. Most of the light in narrow spread LED is directedwithin the mask opening.

In the present embodiment, the number of LEDs can be increased ordecreased on an LED by LED basis. There is no need to reduce or increasethe number LEDs in proportion to the number of clusters as there wouldbe necessary if a MCZE 3 were used. The LEDs can be redistributed on thePCB or in the desired shape based on their light output as necessary oras desired.

The optical elements 25 may be spherical as shown in FIG. 12A. Thespherical optical elements direct the light in every direction. Thissymmetrical diffusing pattern is preferred for symbols such as arrowswhich may be used in any orientation, such as left arrow, right arrow,and straight-ahead arrow.

Alternatively, the optical elements 25 can be shaped to direct thelight. As shown in FIG. 12B, the optical elements 25 can be arcs whichredirect the light down. This embodiment would be preferred for a symbolwhich has a known orientation such as a pedestrian symbol. However, itcould be used with any type of symbol. While FIG. 12B shown opticalelements that redirect the light along the vertical axis, the opticalelements could be oriented to direct the light in the horizontaldirection or any desired direction as dictated by the application.

To allow directional signals to be used in any orientation, withoutrequiring changes to the internal components, the light patterngenerated by the optical elements 25 may be spherically symmetrical asseen in FIG. 12A allowing the assembled housing to be turned in anydirection to orient, for example, a signal arrow as desired. Asymmetrical optical design focusing the light output along the axis beamof the housing with minimal spreading allows the housing to be turned inany direction without losing the correct display aspect. An asymmetricaloptical design as seen in FIG. 12B may be used to minimize sun phantomeffect and/or meet industry specifications related to light distributionfor the display aspect of traffic signals.

The distance H between the MCZE 3 and the PCB 5 is approximately 1inches in a standard twelve-inch signal (FIG. 1). For designs where thesymbol may be fully illuminated by a shorter distance between the LEDs 8and MCZE 3, standoffs or shallower housings may be used. The properdistance allows the LEDs 8 to fully illuminate each optical segment 18without creating overlap, noticeable shadows or dark areas. Theresulting light beam from the signal may be changed by moving the PCB 5with respect to existing optical components (changing H) therebychanging the light output distribution. This spacing also allows use oflight degradation sensor circuitry as described in applicant's Ser. No.09/827,429 application incorporated herein.

As shown in FIG. 9, reflectors 23 may be used to further decrease thenumber of LEDs 8 required to create a desired LED signal light outputlevel. The reflector 23, lowers the amount of light emitted outside ofthe intended light emission pattern 20 by redirecting light normallyescaping through the side of an LED 8. The reflector may also beconfigured to redirect light which reflects under total internalreflection conditions within the LED housing. A second reflectionsurface of the reflector may by aligned with the increased exit angle ofthe total internal reflection light component. Because the angle ishigher than that of light escaping sideways from the LED housing, thesecond reflector surface appears as a step back in the first reflectionsurface and does not degrade the first surface's ability to redirect thesideways escaping light component. The extra materials cost of thereflector 23 is recouped by the lowered number of LEDs 8 required andthe lower operating costs due to reduced energy consumption. Thereflector(s) may be configured around individual LEDs or clusters ofLEDs. A channel shaped reflector 23 allows a limited cross-over of thelight emitted between nearby LEDs, lessening the change to the displayaspect if one or more of the individual LEDs fails.

The size of the PCB 5 may be determined by the smallest circle,rectangle or other shape that will encompass the desired LED pattern,thus saving material costs by minimizing the size of the PCB 5. Wherearrow symbols are being displayed, the arrow form may be cut from a bulkPCB panel 22 cut out as shown in FIGS. 6A and 6B, minimizing the PCBmaterial cost. Power supply and light degradation sensor circuitry maybe located on the single PCB 5 in the area B.

Other embodiments of the present invention include but are not limitedto pedestrian signals, pedestrian signals with countdown displays,informational signals including emergency exit signs, and any other formof LED symbol signal which would otherwise suffer from the “pixeleffect”. In the case of pedestrian signals or other large graphicalsymbols the cover may be omitted and or integrated with the mask, thediffusion surface located, for example on an inner surface of theoptical elements 18 or on the signal's external surface.

This invention is entitled to a range of different embodiments and theirequivalents, and is to be limited only by the scope of the followingclaims.

1. A LED Symbol signal, comprising: at least one Led, mounted on aprinted circuit board, arranged in a housing with an open end; the openend covered by a mask with at least one hole defining the symbol and acover, with a plurality of optical elements substantially covering aninner face of the cover, wherein: said optical elements have a pitch,and a ratio of the pitch to a width of the symbol at the inner surfaceis less than 1:2.
 2. The signal of claim 1, wherein the ratio is lessthan 1:4.
 3. The signal of claim 1, wherein the ratio is less than 1:4.4. A LED symbol signal, comprising: at least on LED, mounted on aprinted circuit bard, arranged in a housing with an open end, the openend covered by a mask with at least one hole defining the symbol, and acover having an inner face with a diffusion surface, the cover sealingthe open end of the housing, wherein a light distribution pattern issymmetrical.
 5. A LED symbol signal, comprising: at least on LED,mounted on a printed circuit bard, arranged in a housing with an openend, the open end covered by a mask with at least one hole defining thesymbol, and a cover having an inner face with a diffusion surface, thecover sealing the open end of the housing, wherein a light distributionpattern is asymmetrical about either the horizontal or the verticalaxis.
 6. A LED symbol signal, comprising: at least on LED, mounted on aprinted circuit bard, arranged in a housing with an open end, the openend covered by a mask with at least one hole defining the symbol, and acover having an inner face with a diffusion surface, the cover sealingthe open end of the housing, wherein: said optical elements have a pitchand a ratio of the pitch and a width of the symbol at the diffusionsurface is less than 1:2.
 7. The signal of claim 6, wherein the ratio isless than 1:4.
 8. The signal of claim 6, wherein the ratio isapproximately 1:10.